1. Field of the Invention
This invention relates to a tee nut and particularly to a tee nut having a female thread formed on the inner peripheral surface of a hollow shaft portion and a plurality of pawls formed on a flange projecting outwardly from one end of said shaft portion.
2. Background Information
A conventional tee nut 1 of interest to the invention is shown in a perspective view in FIG. 6. FIG. 7 is a plan view of the tee nut 1.
The tee nut 1 is integrally made of a metallic material, comprising a shaft portion 2 and a flange portion 3 outwardly projecting from a first end of said shaft portion 2. The shaft portion 2 is in the form of a hollow cylindrical body internally formed with a female thread 4.
The flange portion 3 has two pairs of pawls 5 and 6, and 7 and 8 extending from a second end opposite to said first end, and opposed to each other radially of the flange portion 3. Of these pawls 5 to 8, those forming pairs, i.e., 5 and 6, and 7 and 8, are constructed by forming pairs of cuts extending in mutually opposite directions in the peripheral edge of the flange portion 3 to form tongues and bending said tongues at the ends of the cuts.
Such tee nut 1 is fixed to a member to be secured, such as wood, by inserting the shaft portion 2 into a hole drilled prior to the inserting in said member and driving the pawls 5 to 8 into the member. When the tee nut 1 is fixed to the member in this manner, the rotation of the tee nut 1 is inhibited and a threaded member, such as a bolt, can be threadedly engaged with the female thread 4 formed in the inner peripheral surface of the shaft portion 2.
Such tee nut 1 is generally called a "hopper feed tee nut", because the tee nut 1 shown in FIGS. 6 and 7 can be smoothly moved along a feed track installed on a fixing machine for fixing the tee nut 1 to the wood. The smooth movement permits an automatic feeding of the nuts 1 to an insertion tool. In addition, the details of one type of hopper feed tee nut are disclosed, for example, in British Patent No. 1,157,734.
FIG. 8 shows a plurality of tee nuts 1 being fed along a feed track 9. The feed track 9 has a guide rail 10 of C-shaped cross section. Another guide rail, not shown, is symmetrically disposed in opposed relation to the guide rail 10, and the tee nuts 1 are moved along the feed track 9 with the flange portions 3 received in these guide rails 10 and with the pawls 5 to 8 positioned between said guide rails 10. The feed track 9, as shown in FIG. 8, is often bent, whereby the tee nuts 1 are caused to assume desired positions so that the shaft portions 2 are disposed to be inserted into holes formed in the member to which the nut is to be inserted.
However, when the tee nuts 1 are moved along the feed track 9, particularly when they are moved along a bent portion of the feed track 9, the tee nuts 1 tend to ride on each other, as shown in FIG. 9. This often causes misalignments or clogging of the feeding of the tee nuts 1 by the feed track 9.
The phenomenon in which the flange portions 3 ride on each other can be prevented to some extent by decreasing the size of the clearances given to the flange portions 3 in the guide rails 10 constituting the feed track 9. Such decrease in the size of the clearances, however, causes the frictional resistance between the flange portions 3 and the guide rails 10 to increase to the extent of making it impossible to move the tee nuts 1 smoothly along the feed track 9.